This kind of fuel pump includes an inner rotor having outward teeth, an outer rotor having inward teeth that engage with the outward teeth, and a casing that houses these rotors. The outer rotor is disposed eccentrically with respect to the inner rotor. Then, when the inner rotor is rotated, this rotation force is transmitted from the outward teeth to the inward teeth and the outer rotor also rotates. When both rotors rotate in this manner, the capacity of a pump chamber formed between the outward teeth and the inward teeth changes. As the capacity of the pump chamber increases, fuel is sucked from an intake port into the pump chamber, and then as the capacity of the pump chamber decreases, the fuel is compressed in the pump chamber and then discharged from a discharge port (refer to JP 2013-60901 A).
Further, conventional pumps include a cylindrical shaped housing that houses the casing therein. Typically, the casing is fixed to the housing by press fitting the casing in a cylindrical inner portion of the housing.